Protection of power distribution systems involves detecting, locating and initiating the removal of a fault from the power system. Identifying the location of faults is an important process. Protective relays are extensively used for major protective functions. Protection systems and circuit breakers are installed at strategic locations along the feeder for the purpose of detecting faults that cause excess current to flow and to automatically disconnect them from the source. Manual operations are usually required to isolate the faulty section and this can take several hours during which time many customers are without electricity.
Time grading techniques are often used to minimize the number of customers disconnected when isolating a fault. Time graded protective systems have protective devices in successive zones that are arranged to operate in times which are graded through the sequence of equipment so that upon the occurrence of a fault only those relevant to the faulty zone complete the tripping function. A disadvantage of time grading schemes is that they are slow to identify faulted zones and due to the time separation required and it is assumption that there is a single source feeding the system. This method is not suitable when dealing with multiple variable sources like wind and solar generation and will require continual adaptive setting changes in real time.
A number of systems exist dealing with fault detection of circuits in power distribution networks such as those described in U.S. Pat. Nos. 6,603,649; 6,687,573; 7,636,616; 7,773,360; 2008/0024142; and 2009/0290275, all of which are incorporated herein by reference.
There is a need in the art for a scheme that can clearly detect a faulted zone in a shorter time and with less impact on the connected power grid and that is also immune to the effect of the introduction of distributed generation in distribution feeder networks. The present invention addresses those needs.